Asynchronous Transfer Mode is a high-speed, scalable cell switching protocol that breaks packets down into fixed 53-byte cells, well suited for quality of service transmissions of data, voice, and video.

BackPressure

The technique used for notifying end-nodes of a busy condition by sending an Etherent jam signal requesting that end-nodes refrain from tansmitting until buffers are emptied.

Bad Packet

A corrupted or damaged data packet that is often re-transmitted by other Etherent switches (particulary cut-through switches) chewing up valuable bandwidth.

Bandwidth

The transmission capacity of a data channel, often referred to as the network's speed (for Ethernet this is 10Mbps) can be thought of as the number of open lanes on a highway. See the Glossary item on Ethernet standards and speeds for more information.

Bottleneck

Any point or intersection in a network, often internet working devices such as switches, that could cause a data traffic jam when several points of transmission compete for full bandwidth.

Bridge

An unintelligent MAC-layer device that connects two similar network types together to form an internetwork.

Bursty Traffic

LAN traffic that requires very high bandwidth for short periods of time and relatively low bandwidth between tranmissions.

Client/Server

A model of distributed processing in which the client workstation is the requesting machine and the server is the supplying machine; processing is distributed between client and server requiring reliable communication between them for application integrity.

Cross-bar Switch

A first generation switch architecture designed for optimal point-to-point communication that inherently creates bottlenecks and introduces non-deterministic delay, not suitable for multimedia, client/server, or mission-critical environments.

Cut-through Switch

A type of switch that examines only the destination address of the Etherent header before it begins to send the packet on its way; may introduce network errors by forwarding bad packets without checking for errors.

Data Packet

A vairable-length slice of data formatted with a destination and source address, among other things, that is understandalbe to all devices supporting a particular protocol, such as Ethernet.

Ethernet with only two nodes per segment running at double-speed, or 20Mbps, since nodes have no contention issues and can transmit and receive simultaneously, provides a mechanism for higher-bandwidth connections to servers and end-nodes without requireing reconfiguration or new technology deployment.

IEEE 802.1d

The industry standard for eliminating broadcast storms at the MAC layer in meshed networks that have redundant or cyclical paths.

Jitter

A flickering transmission signal or display caused by non-deterministic delay common to packet transmission devices and unacceptable for multimedia or client/server applications.

Latency

Delay introduced at any point in a network, due to processing, usually by an internetworking device such as a switch or router; non-deterministic delay causes network jitter, fixed-latency devcies introduce small and predictable delays at all levels of traffic load.

MAC Layer

The second layer of the Open System Interconnect (OSI) Model which bridges and switches use to determine the destination device; by contrast, routers use higher-level information of the OSI Layer 3, or Network Layer, to route data.

NAS

Network Access Storage is defined as a product that sits between the application server and the file system. The product could be hardware, software, or both.

Next-generation Technology

A quantum leap over first-generation technology because it has the benefit of learning from real-world situations and provides enhancements to previously deployed technology.

Non-blocking Switch

The ability of a switch to continue to accept transmissions from all ports at all times, effectively removing bottlenecks (blocking) at the switch port level.

Non-deterministic Delay

A variable time period during which data packets are delayed when encountering a network bottleneck or vairable-length packets; introduces jitter which is unacceptable in client/server and multimedia environments.

Redundacy

Increasing network reliability by providing multiple data paths or components so that a secondary route or device could take over in the event of the primary's failure.

SAN

Storage Access Network is defined as an architecture that sits between the application server and the file system. As such, a SAN is a separate network that connects storage and servers consisting of NAS devices.

Segmentation

Breaking up large Ethernet networks into smaller networks that are then connected by an internetworking device such as a a switch, router or bride; increases overall network bandwidth, isolating traffic by keeping unnecessary packets off segments.

SNMP

Simple Network Management Protocol, the industry standard way for devices to communicate with network management platforms.

Store-and-forward

A mechanism in which data packets are received in their entirety by a switch and examined for consistency before they are sent to their destination; reduces network errors by discarding bad packets but increases latency; also required to translate between networks of different speeds or types.

Switch

An internetworking device that intelligently segments networks to increase overall bandwitdth, isolate traffic, and provide an interface to high-speed networks. A typical Switch will be either a store-and-forward device or a cut-through device, one or the other, but not at the same time.

Virtual Collision

A fake collision generated by the LANbooster to implement the BackPressure-based flow control mechanism.

Date of Last Revision: 17 December 2001. Extracted from Switching Technology in the Local Area Network by Mathias hein and David Griffiths and Computer Technology Review Magazine 2000.